Journal of Thermal Analysis and Calorimetry
Volume/Issue:
Volume 89: Issue 3
The kinetics of thermo-oxidative humic acids degradation studied by isoconversional methods
Authors:
D. Válková BUT Faculty of Chemistry Purkyñova 118 Brno Czech Republic

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J. Kislinger BUT Faculty of Chemistry Purkyñova 118 Brno Czech Republic

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M. Pekař BUT Faculty of Chemistry Purkyñova 118 Brno Czech Republic

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J. Kučerík BUT Faculty of Chemistry Purkyñova 118 Brno Czech Republic

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Pages:
957–964
Online Publication Date:
04 Sep 2007
Publication Date:
01 Sep 2007
Article Category:
Research Article
DOI:
https://doi.org/10.1007/s10973-007-8437-5
Keywords:
DSC; lignite humic acids; isoconversional methods; stability
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Abstract  

Humic acids represent a complicated mixture of miscellaneous molecules formed as a product of mostly microbial degradation of dead plant tissues and animal bodies. In this work, lignite humic acids were enriched by model compounds and the model-free method suggested by Šimon was used to evaluate their stability over the whole range of conversions during the first thermooxidative degradation step. The kinetic parameters obtained were used to predict the stability at 20 and 180�C, respectively, which served for the recognition of processes induced by heat and those naturally occurring at lower temperatures. Comparison of the conversion times brought a partial insight into the kinetics and consequently into the role of individual compounds in the thermooxidative degradation/stability of the secondary structure of humic acids. It has been demonstrated that aromatic compounds added to humic acids, except pyridine, increased stability of humic acids and intermediate chars. The same conclusion can be drawn for acetic and palmitic acids. Addition of glucose or ethanol decreased the overall humic stability; however, the char of the former showed the highest stability after 40% of degradation.

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Cover Journal of Thermal Analysis and Calorimetry
Journal of Thermal Analysis and Calorimetry
Print ISSN:
1388-6150
Online ISSN:
1572-8943

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation		 1969
Volumes
per Year		 1
Issues
per Year		 24
Founder Akadémiai Kiadó
Founder's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher		 Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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